과공정 Al-Si 합금의 내마모성 연구

김헌주,정운재 ( Heon Joo Kim,Woon Jae Jung ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.6

N/A The wear resistance of Hyper-eutectic Al-Si alloy, have recently been noticed as a new automobile material, was investigated. For the purpose of developing wear resistant Al-Si alloy, some factors which attribute to wear resistance are examined as follows; refinement of primary Si particle during solidification, and effect of refinement on wear resistance and other mechanical properties. The most effective refinement was accomplished by adding both NaF and S, and this improve wear-resistance in abrasive wear type. The wear losses of specimens cast in metal mold were ruduced to 80% of those in sand mold. T6 heat treatment increases hardness, which resulted in reduction of wear loss about 3∼18 %.

고압 금형 주조용 Al-4 wt%Mg-0.9 wt%Si계 합금의 인장특성에 미치는 Fe, Mn함량의 영향

김헌주 ( Heon Joo Kim ) 한국주조공학회 2013 한국주조공학회지 Vol.33 No.3

Effect of Fe and Mn contents on the tensile properties of Al-4 wt%Mg-0.9 wt%Si alloy system has been studied. Common phases of Al-4 wt%Mg-0.9 wt%Si alloy system were α-Al, Mg2Si, α-Al12(Fe,Mn)3Si and β-Al5FeSi. As Fe content of Al-4 wt%Mg-0.9 wt%Si alloy system increased from 0.15 wt% to above 0.3 wt%, β-Al5FeSi compound appeared. When Mn content of the alloy increased from 0.3 wt% to 0.5 wt%, morphology of plate shaped β-Al5FeSi compound changed to chinese script α-Al12(Fe,Mn)3Si. As Fe content of Al-4 wt%Mg-0.9 wt%Si-0.3 wt%Mn alloy increased from 0.15 wt% to 0.4 wt%, tensile strength of the as-cast alloy decreased from 191 MPa to 183 MPa and, elongation of the alloy also decreased from 8.0% to 6.2%. Decrease of these properties can be explained as the formation of plate shape, β-Al5FeSi phase with low Mn/Fe ratio of the alloy. However, when Mn content of Al-4 wt%Mg-0.9 wt%Si-0.3 wt%Fe alloy increased from 0.3 wt% to 0.5 wt%, tensile strength of as-cast alloy increased from 181 MPa to 194 MPa and, elongation of the alloy increased from 6.8% to 7.0%. These improvements attribute to the morphology change from β-Al5FeSi phase to chinese script, α-Al15(Mn,Fe)3Si2 phase shape-modified from with high Mn/Fe ratio of the alloy.

고신율 금형주조용 Al-9wt%Si-Mg계 합금의 주조특성에 미치는 Fe, Mn함량의 영향

김헌주 ( Heon Joo Kim ),정창열 ( Chang Yeol Jeong ) 한국주조공학회 2013 한국주조공학회지 Vol.33 No.6

Effect of Fe and Mn contents on the castability of Al-9wt%Si-xMg-yFe-zMn alloy has been studied. The alloy was composed of α-Al phase, Al+eutectic Si phase, β-Al5FeSi compound and chinese script α-Al15(Mn,Fe)3Si2 compound. β-Al5FeSi and α-Al15(Mn,Fe)3Si2 compounds assumed to effect the fluidity and shrinkage behaviors of the alloy during solidification due to the crystallization of α-Al15(Fe,Mn)3Si2 and β-Al5FeSi compounds above eutectic temperature. As Fe and Mn contents of Al-9wt%Si- 0.3wt%Mg system alloy increased from 0.15wt% to 0.6wt% and from 0.3wt% to 0.7wt%, fluidity of the alloy decreased by 5.7% and 3.3%, respectively. And as Mg content of Al-9wt%Si-0.45wt%Fe-0.5wt%Mn system alloy increased from 0.3wt% to 0.4wt%, fluidity of the alloy decreased by 8.6%. When Fe content of the alloy increased from 0.15wt% to 0.6wt%, macro shrinkage ratio decreased from 6.1% to 4.1%, and micro shrinkage ratio increased from 0.04% to 0.24%. Similarly, Mn content of the alloy increased from 0.3wt% to 0.7wt%, macro shrinkage ratio decreased from 6.0% to 4.5% and micro shrinkage ratio increased from 0.12% to 0.18%. Judging from the castability of the alloy, Al-9wt%Si-0.3wt%Mg alloy with low content of Fe and Mn, 0.1wt% Feand 0.3wt% Mn, is recommendable.

대학 인재상을 반영한 대학생 인성역량 평가지표 개발 : H 대학 사례연구

김헌주(Heon Joo Kim) 한국자료분석학회 2020 Journal of the Korean Data Analysis Society Vol.22 No.5

The aim of this study is to define several sub-concepts of the personality competency which is one of several personal abilities established through education at the H university. We also develop several tools to measure such sub-concepts which may show the changes of the personality competency. In the preliminary survey, we carry out the study on the basic concepts of the personality competency and several sub-concepts. We discuss these with the university expert group members and fix 10 sub-concepts. We develop and confirm 40 questions that measure the sub-concepts of personality competency through two preliminary studies for the H university students. These 10 sub-concepts of personality competency pursued in the H university are sincerity, self-respect, moderation, consideration and etiquette, sacrifice, conscience, (social) justice, honesty, responsibility and cooperation. The importance of the 10 sub-concepts are all considered the same. Finally, for the developed 40 questions, the reliability and validity of the questions are examined for all students in 2017, and is suggested that the developed questions could be used as a tool to measure the personality competencies of university students. 본 연구의 목적은 H 대학에서 교육을 통해 이루고자 하는 여러 가지 역량 중의 하나인 인성을 구체적으로 설명할 수 있는 하위 개념을 정의하는 것이다. 또한 정의된 각 하위 개념을 측정할 수 있는 측정 문항을 개발함으로 교육을 통해 인성 역량이 어떻게 변화하였는가를 측정할 수 있도록 제안하는 것이다. 대학 교육을 통해 향상될 수 있다고 기대되는 인성의 하위 개념은 H대학에서 인성 교육을 담당하는 전문가 집단의 의견과 선행연구를 통하여 10가지로 정의하였다. 정의된 인성 10가지 하위 개념을 측정할 수 있는 문항 40개를 개발하였으며, 이 문항들은 H 대학 학생들을 대상으로 2차에 걸친 예비조사를 통해 개발하고 확정하였다. H 대학에서 추구하는 인성은 10가지 하위 개념으로 정의할 수 있으며 이는 성실, 자기존중, 절제, 배려 및 예절, 희생, 양심, (사회)정의, 정직, 책임, 협동으로 정리되었다. 하위 개념 10가지의 중요성은 모두 동일한 것으로 간주하였다. 마지막으로 개발된 40개 문항에 대해 2017학번 학생 전체를 대상으로 문항의 신뢰성 및 타당성을 검토하였으며, 개발된 문항을 통해 대학생들의 인성 역량을 측정하는 도구로 활용할 수 있음을 제안하였다.

6061AI 복합재료 마모특성에 미치는 SiC 입자 강화재 체적분율의 영향

김헌주(Heon Joo Kim) 한국열처리공학회 2002 熱處理工學會誌 Vol.15 No.2

N/A In the present investigation wear behavior of the 6061Al composites reinforced with 5, 10, 20% SiC par tides for dry sliding against a SM45C counterface was studied as a function of load and sliding velocity. Sliding wear tests were conducted at two loads(19.6 and 49N) and three sliding velocitiies(0.2, 1 and 2 m/sec) at constant sliding distance of 4000 m using pin-on-disk machine under room temperature. Presence of SiC reinforcement particles in the composites has displayed a transition from mild to severe wear at relatively higher applied load and sliding velocity compare to that of the matrix metal. As the volume fraction of SiC particles increased, the transition moved to a more severe wear conditions. Eventually, mild wear prevailed at a most severe wear conditions in this study, that was 49N load and 2 m/sec sliding velocity in 20% SiC partide/6061Al composite.

고압 금형주조용 Al-9%Si-0.3%Mg 합금의 Fe, Mn 함량이 인장특성에 미치는 영향

김헌주 ( Heon Joo Kim ) 한국주조공학회 2011 한국주조공학회지 Vol.31 No.1

Effect of Fe and Mn contents on the tensile properties has been studied in Al-9wt%Si-0.3wt%Mg alloy. As Fe content of Al-9wt%Si-0.3wt%Mg-0.5wt%Mn alloy increased from 0.15wt% to 0.45wt%, tensile strength of as-cast alloy decreased from 192 MPa to 174 MPa, and elongation of the alloy also decreased from 4.8% to 4.2%. Decrease of these properties can be explained as the formation of plate shape, β-Al5FeSi phase with high Fe/Mn ratio of the alloy. However when Mn content of Al-9wt%Si-0.3wt%Mg-0.45wt%Fe alloy increased from 0.3wt% to 0.5wt%, tensile strength of T6 aged alloy increased from 265 MPa to 275 MPa, and elongation of the alloy increased from 2.3% to 3.6%. These improvements attribute to chinese script, α-Al15(Mn,Fe)3Si2 phase shape-modified from β-Al5FeSi phase with low Fe/Mn ratio of the alloy.

AISI 51B20 보론첨가강의 경화능에 미치는 오스테나이트화 온도의 영향

김헌주 ( Heon Joo Kim ),박무용 ( Moo Yong Park ) 한국열처리공학회 2010 熱處理工學會誌 Vol.23 No.6

Effect of hardenability, grain size and microstructural change according to the change of austenitizing temperature was analyzed in Jominy hardenability test of AISI 51B20 steel. Grain growth was small, 7㎛ and 12㎛ austenite grain sizes at austenitizing temperature of 900℃ and 1000℃, respectively, while rapid grain growth was observed up to 30㎛ austenite grain size at austenitizing temperature of 1100℃. As austenitizing temperature increased from 900℃ to 1100℃, hardenability in the region within 15 mm from end-quenched surface decreased due to the grains growth of bainite and martensite mixture, on the other hand the hardenability in the region exceeding 15 mm from end-quenched surface increased. Increased hardenability was attributed to different microstructures; pearlite, fine pearlite and bainite, and bainite and martensite structures at austenitizing temperature of 900℃, 1000℃ and 1100℃, respectively.

AC2B 알루미늄 주조합금의 응고균열 강도에 미치는 금형 예열온도의 영향

김헌주 ( Heon Joo Kim ) 한국주조공학회 2014 한국주조공학회지 Vol.34 No.5

The effect of the mold preheat temperature on the solidification crack strength was investigated in AC2B aluminum alloy. A tension type apparatus as part of a solidification crack test which could measure the stress-strain relationship quantitatively was utilized. The evaluation of the solidification crack strength with varying mold preheat temperatures was performed by the test procedure established in this research. When the mold preheat temperatures were 250℃, 150℃ and 50℃, the solidification crack strengths were found to be 7.8 Kgf/cm2, 12.9 Kgf/cm2 and 28.6 Kgf/cm2, respectively. In the same way, when the mold preheat temperatures were 250℃, 150℃ and 50℃, the corresponding temperatures of the failure sites were 610℃, 600℃ and 571℃, and the calculated solid fractions were 14.0%, 29.3% and 50.8% when the specimens failed, respectively. The solidification crack strength increased in proportion to the solid fraction of the failure site. The solidification crack strength obtained in this test is assumed to reflect the effects of metallurgical factors on the thermo-plastic characteristics of a solidifying alloy such as the grain size of the solid, the grain morphology, and the distribution of solid grain.

AISI 51B20강의 인장 및 충격특성에 미치는 오스테나이트화 온도와 퀜칭,템터링 온도의 영향

김헌주 ( Heon Joo Kim ) 한국열처리공학회 2011 熱處理工學會誌 Vol.24 No.6

Abstract Effects of microstnictura change, tensile properties and impact property according to the change of austenitizing temperature and tempering temperature of AISI 51B20 steel were examined. Regardless of austenite grain size, lath martensite with needle and packet shapes was found at tempering temperature of 300℃~400℃. The needles of lath martensite changed to parallel packet at tempering temperature of 450℃~600℃. As tempering temperature increased, tensile strength, yield strength and hardness decreased, while elongation, ratio of reduction area and Charpy impact energy increased. Grain size increased when quenching temperature was 930℃. Grain size had prominent effect on the mechanical properties of AISI 51 B20 steel. Ratio of tensile strength/yield strength and yield strength autenitized at 880℃ followed by tempering at 350℃-450℃ showed higher values than that of autenization at 930℃ due to fine grain size. (Received September 18, 2011; Revised October 21. 2011; Accepted November 2, 2011)

주조용 Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe 합금의 공정Mg2Si 개량과 주조특성에 미치는 Sc, Sr 첨가원소의 영향

김헌주 ( Heon Joo Kim ) 한국주조공학회 2015 한국주조공학회지 Vol.35 No.6

The effects of Sc and Sr elements on the modification of the eutectic Mg2Si phase and the castability were investigated in the Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe alloy. Measurements of the cooling curve and microstructure observations were performed to analyze the additional effects of Sc and Sr minor elements during the solidification process. A prominent effect found on the modification of the eutectic Mg2Si phase with additions of the Sr and Sc elements. Here, a fine eutectic Mg2Si phase and a decrease in the growth temperature of the eutectic Mg2Si phase were evident with an addition of Sc element up to 0.2 wt%. The growth temperature of the eutectic Mg2Si phase decreased and the effect on the modification of the eutectic Mg2Si phase increased with the addition of Sr element up to 0.02 wt%. The addition of 0.02wt%Sr had the strongest effect on the modification of the eutectic Mg2Si phase, and the resulting microstructure of the eutectic Mg2Si phase was found to have a fibrous morphology with a decreased aspect ratio and an increased modification ratio. Fluidity and shrinkage tests were conducted to evaluate the castability of the alloy. The addition of 0.02wt%Sr effectively increased the fluidity of the alloy, while an addition of Sc did not show any effect compared to when nothing was added. The maximum filling length was recorded for 0.01wt%TiB-0.02wt%Sr owing to the effect of the fine α-Al grains. The macro-shrinkage ratio decreased, while the micro-shrinkage ratio increased with the addition of various eutectic modifiers. The highest ratio of micro- shrinkage was recorded for the 0.02wt%Sr condition. However, the total shrinkage ratio was nearly identical regardless of the amounts added in this study.